The cardiovascular surgery is a field in which a surgical error is highly likely to be a direct cause of an operational death, and thus, requires high skills in an operation. One of such cardiovascular surgeries is a coronary-artery bypass surgery. A coronary-artery bypass surgery is a surgical technique in which when a part of coronary arteries extending around a heart is narrowed, a peripheral side of the narrowed part and another blood vessel part are connected by an alternative blood vessel called a graft to ensure blood flow.
For young doctors, it is difficult to gain experience in clinical practice, and thus, for improvement in the aforementioned surgical skills (techniques), an environment enabling efficient training is required. Here, as an example of training for improving the techniques of young surgeons, there is a training using a heart of a pig as a heart of a human, which is conducted under supervision of a skilled surgeon. However, such training using an organ of an animal is troublesome in storage and problematic not only from a hygiene perspective but also in ethics because of use of a living tissue. Accordingly, due to such problems, there is a demand for using not a living tissue but an artificial training tool for aforementioned technique training.
There is a known blood vessel model formed by implanting a simulated blood vessel in a position close to a front surface of a gelatinous object simulating a tissue of an animal (see patent document 1). This blood vessel model is intended for use in practicing a technique to insert an injection needle or a blood collection needle.
However, where the blood vessel model according to patent document 1 is used for training for coronary-artery bypass surgery, such training cannot be conducted in realistic conditions. In other words, a real blood wall is consistently subject to an inner pressure caused by a blood pressure in a physiological state, and for balance with the inner pressure, a stress exists in the blood vessel tissue. Thus, in performing an anastomosis, a front surface of a blood vessel wall is incised in a direction of the axis of the blood vessel, and the incised part swiftly expands in a circumferential direction of the blood wall. However, in the blood vessel model, as opposed to a real blood vessel, no such stress exists in the simulated blood vessel, and thus, even if a blood vessel wall of the simulated blood vessel is incised, a mere slit is formed, and no force that expands the slit in the circumferential direction acts thereon. In other words, in a real operation, procedures such as sewing, ligation and anastomosis are performed in a state in which an incised part of a blood vessel is expanded, and thus, it is difficult to conduct training close to a real situation if the blood vessel model is used as it is. Therefore, for performing a training close to a real situation using the blood vessel model, a tool for expanding an incised part of a blood vessel is separately required, and also adjustment of the tool to provide a proper expansion condition is required, disabling doctors or medical students to easily perform procedure trainings.
Therefore, the present inventors already proposed a blood vessel model that can be approximated to a real blood vessel without using any other tool when a simulated blood vessel is incised (see patent document 2). As illustrated in FIG. 7, such blood vessel model 50 includes an artificially-formed simulated blood vessel 51, and a base 52 supporting the simulated blood vessel 51. The base 52, which is a laminated body obtained by putting two upper and lower layers of elastic material together, includes an upper first member 54 in which a part of a simulated blood vessel 51 is buried, and a second member 55 put on a lower side of the first member 54. In the first member 54, a tensile stress in a direction in which a diameter of the simulated blood vessel 51 increases. Accordingly, when a blood vessel wall of the simulated blood vessel 51 is incised in a direction of an axis of the simulated blood vessel 51, the simulated blood vessel 51 is swiftly opened in a circumferential direction thereof.
The blood vessel model 50 is manufactured according to the procedure illustrated in FIG. 8. In other words, as illustrated in FIG. 8(A), while left and right sides of the first member 54 being flexed downward in the Figure, the bottom surface thereof is bonded to the upper surface of the second member 55 in the Figure along the upper surface, and consequently, as illustrated in FIG. 8(B), a tensile stress directed outward, which is the horizontal direction in the Figure, is generated inside the first member 54. As a result, the tensile stress in the diameter-increasing direction is imparted to the simulated blood vessel 51.    Patent Document 1: Japanese Patent Laid-Open No. 11-167342    Patent Document 2: Japanese Patent Laid-Open No. 2007-316343